Field of the Invention
The present invention relates to a wavelength tunable laser device and an optical coherence tomography apparatus using the wavelength tunable laser device.
Description of the Related Art
In recent times, a wavelength tunable laser device that can change a wavelength of laser light emitted therefrom is attracting attention. As the wavelength tunable laser device, a vertical cavity surface emitting laser (VCSEL) device is proposed (Connie J. Chang-Hasnain, Fellow, IEEE, “Tunable VCSEL”, IEEE Journal on Selected Topics in Quantum Electronics, Vol. 6, No. 6, pp. 978-987, 2000.). In the vertical cavity surface emitting laser device, through displacement of one of two reflectors, an interval between the two reflectors is changed, thereby changing an oscillation wavelength, that is, a resonance wavelength, of laser light. As a movable portion (movable mechanism) configured to displace a reflector, one to which a micro electro mechanical systems (MEMS) technology is applied has been proposed. A vertical cavity surface emitting laser device to which the MEMS technology is applied is referred to as a MEMS-VCSEL.
The MEMS-VCSEL can continuously change the wavelength. Further, in the MEMS-VCSEL, the movable portion is minute. Therefore, the movable portion can be displaced at high speed, and thus, the wavelength can be changed at high speed. Further, the MEMS-VCSEL has low power consumption. Such characteristics of the MEMS-VCSEL attract great attention thereto.